1. Field of the Invention
The present invention generally relates to a liquid dispensing apparatus, and, more particularly, to a new and improved compact, ambulatory infusion pump having an elastomeric bladder for dispensing intravenous or other pharmaceutical drugs to a patient.
2. Description of the Prior Art
Some medical patients need to receive intravenous or other pharmaceutical drugs. These patients are not necessarily restricted to bed or confined to a hospital and consequently, infusion devices have been developed by which such drugs can be dispensed while the patient is ambulatory. Typically these infusion devices or pumps have an outer housing with an elastomeric bladder that is mounted therein on an internal stress mandrel disposed within the housing. When the bladder is being filled with a liquid, such as intravenous drugs, the elastic bladder will expand such that a dispensing pressure will be exerted on the liquid within the expanded bladder. As a result, the fluid can be dispensed out from the bladder via an infusion tube or the like connected to or through the mandrel.
Previously designed infusion pumps tend to be somewhat difficult and costly to manufacture and assemble. In some of these infusion pumps, the elastomeric bladders are prestressed either in the axial or radial directions or in both such directions prior to the introduction of fluid into the bladder. The prestressing of the bladder in this fashion tends to provide a more uniform pressure profile for the liquid being dispensed from the infusion pump and enables a higher percentage of the liquid to be dispensed from within the bladder. However, prestressing of the bladder in this manner tends to make assembly of such infusion devices more difficult. In addition, the manufacturing and assembly of previously designed infusion pumps tend to be costly due at least in part to the number of different component parts that need to be separately manufactured and assembled and the difficulty of assembling and the amount of time required to assemble these components.